Camera diaphragm



July 30, 1940. H. F. TONNIES V CAMERA DIAPHRAGM Filed Dec. 8, 1938 Patented July 30, 1940 mm DIAPHRAGM Hans Ferdinand Tiinnies, Hamburg-Gronflottbek, Germany Application December 8, 1938, Serial No. 244,704

14 Claims.

This invention relates to camera diaphragms and particularly to electrically operated diaphragms for use with photoelectric systems to adjust the efiective lens aperture automatically in accordance with the existing scene'brightness, and preselected values of exposure factors as, for example, emulsion speed, shutter timing, filter factor and/or character of the scene.

Many of the prior proposals for automatic diaphragms are inoperative or impractical for the reason that the photoelectric systems are incapable ofdeveloping power suflicient to actuate the diaphragm members. This faulty design is characteristic of that type of diaphragm which 16 has a single moving coil for operating a plurality of diaphragm members. A diaphragm including independently movable coils that each carry a. diaphragm blade is described and claimed in my prior Patent No.2,051,061, granted August 20 18, 1936, butthis'invention contemplates a mechanical connection between a plurality of pivoted diaphragms that are actuated by one or more moving coils. The mechanical connection insures the simultaneous adjustment of all blades. An object of the invention is to provide an electrically operated diaphragm having a plurality of pivoted blades, an electrical instrument having one or more coils for actuating the plurality of blades, and mechanisms that place substantially no load on the moving system connecting the coil or coils and the blades for simultaneous movement. An object is to provide a diaphragm having a plurality of pivoted blades, an instrument having a coil carrying one of the blades, and mechanical connections of negligible power consumption coupling the coil to the other blades. An object is to provide a diaphragm of the type stated in which the mechanical connections include resilient wires or filaments passing around cylindrical surfaces at the several blades, the power consumed in coiling one end of the wire or filament about its cylindrical surface in the turning the blades being offset by the power given up as the other end of the resilient wire or filament is uncoiled.- Further objects are to provide automatic diaphragms including an instrument having a pivoted coil carrying one diaphragm blade, a plurality of addltional diaphragm blades each mounted on a shaft, and mechanical connections between the coil and the additional blades, the mechanical connections including resilient wires or filaments anchored to levers-or to small pulleys carried by the coil and the several blade shafts. These and other objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawing in which:

Fig. l is an enlarged side elevation of an instrument and blade members constituting one 5 embodiment of the invention;

Fig. 2 is a transverse section approximately on line 2-2 of Fig.1;

Fig. 3 is an enlarged fragmentary view, similar to Fig. l but omitting the instrument magnet 10 and the blades, of another form of mechanical coupling between the instrument coil and the pivotal supports for certain blades;

Fig. 4 is an enlarged elevation, partly in section, of one of the blade'supports; and 15 Fig. 5 is an elevation of an embodiment in which more than one moving coil is used to actuate the set of mechanically coupled blades.

In the drawing, the reference numeral I identifies the permanent magnet structure of an 20 electrical measuring instrument which includes a soft iron core 2 and a coil 3 pivotally mounted on jewel bearings l for angular movement about the core. The restoring springs and electrical connections to the coil are not shown but may be 25 of known or desired design. It is to be understood that the parts are shown on an enlarged scale for clearness-of illustration and that recently developed magnet alloys of high retentivity permit the manufacture of instruments 30 of small size that are well adapted for the operation of an automatic camera diaphragm.

The axis of the coil 3 and a plurality of shafts 5, 5 are uniformly spaced in cylindrical symmetry about and parallel to the axis of the 35 camera lens L.. Each stafi 5 is supported by a substantially frictionless bearing 6 such as the jewel bearings commonly used in measuring instruments. The coil and each staff 5 have se-- cured thereto a diaphragm blade I of blackened aluminum or mica, the blades being of sickle shape and having efl'ective edges 8 that lie beyond the lens L when the blades are fully opened and move progressively into the light passages as the blades are turned counterclockwise. Each blade extends beyond its pivotal support and carries a balance weight 9. The turning range of the coil may be about to and the effective lens aperture is slowly and progressively varied with the displacement of the blades.

The mechanism for transmitting motion from the coil 3 to the shaft 5 comprises actuating members l0 secured to the coil and shafts and connected by cables in the form of resilient filaments H such as wires. ribbons, twisted 55 spider web threads, thin silk threads, or human hair. As shown in Figs. 1 and 2, the actuating .but the power consumption for bending each fillower filament H, to impart the same angular movement to the shafts 5 and theirblades I. It is to be noted that one end of each filament H is wound upon a cylindrical surface as the other end is unwound in the angular movement of the shafts and-coil. This bending of a resilient filament about a'cylindrical surface places a mechanical load upon the moving coil system since some force must be exerted to fiex the filament,

ament is substantially neutralized as the opposite end of that filament uncoils from its stud. It

is impossible to obtain filaments of such high flexibility as to require no force for bending the same, but initially straight resilient filaments impose substantially no load on the moving system when, as described, one end is wound from a cylindrical surface as its opposite end is wound upon a similar cylindrical surface. t

The actuating-members I 0' of the motion transmitting system of. Figs. 3 and 4 comprise small pulleys around which the ends of the resilient filaments II are coiled and secured by drops i3 of cement or wax. The curvature of the pulley surfaces is substantially less than that of the studs H .of the previously described construction and the force required to bend the resilient filaments about the pulleys is therefore quite small. The bending or ceiling of the resilient filaments should not be so sharp as to exceed the elastic limit of the material since, if that condition exists', the tendency of the filament to unwind from one pulley will not neutralize the force required to bend the filament about the other pulley.

This resilient filament type of mechanical coupling may be used to insure like displacements of all blades in automatic diaphragms having a moving coil for each blade or the filaments may function both as operating and as displacement stabilizing means in diaphragms having two or more coils for actuating a larger number of blades. A construction of the latter type, as shown in Fig. 5, includes a magnetic system formed by two magnets 2! having unlike poles spaced apart to provide gaps arranged symmetrically with respect to the axis of the camera lens L. Moving coils 23 are pivotally supported in the air gaps and carry small pulleys It, and two shafts, 5"are arranged parallel to the lens axis and in symmetry with, the coil axes. Pulleys Ill on the shafts 5 are connected to the pulleys of the moving coils by fine resilient filaments I/L'anddiaphragm blades 1 are supported by the shafts 5' and the coils. The outer edges 8' of the blades I have approximately the 'shape' of the inner edges 8 of the described sickle shaped blades 1, and the edges 8' move progressively into the light passage of the lens system as the coils 23 move in response to current flow. The symmetrical arrangement of all blade edges 8' with respect/to the lens axis is maintained throughout the range of blade movement by the filaments II that interconnect the several pulleys i0.

The torque developed by the moving coil or coils of a sensitive milliammeter associated with a current-generating photocell is exceedingly minute and it isnot possible for a moving coil to actuate a diaphragm system which imposes an appreciable mechanical load upon the instrument. 'The power consumption is reduced to a minimum by the present invention as the work performed by the instrumentis restricted to the overcomingof the frictional resistance of shafts mounted'in jewel bearings or the like and the internal frictional resistance to bending of a plurality of slightly resilient filaments.

It is to be understood that there is considerable latitude in the design and construction of embodiments of this invention and that many changes which may occur to those familiar with this art fall within the spirit of my invention as set forth in the following claims.

I claim:

1. An automatic diaphragm for use with a camera lens, said diaphragm comprising a plurality of blades, means supporting said blades for pivotal movement about axes parallel to and in cylindrical symmetry about the axis of the camera lens, an electrical measuring instrument having at least one coil supported for pivotal movement, and motion transmitting means including filaments connecting said supporting means to each other and to said coil.

.2. An automatic diaphragm as claimed in claim 1, wherein one of said blades is secured to said coil.

3. In an automatic diaphragm for use with a camera lens, a" plurality of blades, means pivotally supporting said blades, an electrical measuring instrument having a coil pivoted for angular movement about an axis parallel to the axes of said blades, and motion transmitting means connecting said coil to said blades, said motion transmitting means including actuating members, secured to said coil and to said supporting means, and initially straight resilient filaments extending between adjacent actuating members, the actuating members having curved surfaces for engagement by said filaments.

4. A diaphragm mechanism for use with a camera lens, said mechanism comprising-an electrical measuring instrument including a pivotally mounted coil, a plurality of shafts parallel to and with said coil symmetrically located with reference to the axis of the camera lens, diaphragm blades carried by said coil and said shafts, and means coupling said shafts to said coil for actuation thereby.

5. A diaphragm mechanism as claimed in claim 4, wherein each of said blades is of sickle shape with a light-intercepting edge at the side of the lens opening opposite the pivotal axis of the blade.

6., A camera diaphragm comprising a plurality of blades, circumferentially spaced supporting means mounting said blades for pivotalmovement about parallel axes, an electrical instrument having a pivoted coil, and motion transmitting means connecting said supporting means to each other and to said coil; said motion transmitting means including operating members secured respectively to said coil and to each blade aaoaess 8. A camera diaphragm as claimed in claim wherein said operating members have cylindrical surfaces engaging end portions of said resilient filaments, said end portions of the filaments extending tangentially to said cylindrical surface to wind and unwind with the turning movement of said supporting means. i

9. A diaphragm mechanism for controlling the passage of light through a camera lens, said mechanism comprising a plurality of blades, sup'- ports mounting said blades for pivotal movemen about axes parallel instrument having a coil supported for pivotal movement about an axis parallel to the lens axis, and means including resilient filaments for transmitting angulanmovement .of said coil to said blades.

10. An automatic lens diaphragm comprising a plurality of blades pivctally supported for movement about axes parallel to the lens axis, an electrical measuring instrument having a pivoted coil, and motion-transmitting means mechanically connecting said coil to said blades; said means including actuating members secured to the several blades and having cylindrical surfaces, and resilient filamentssecured to adjacent actuating means and in engagement with said cylindrical surfaces.

11. An automatic diaphragm as claimed in claim 10, wherein said motion-transmitting means includes pulleys secured respectively to said coil and to said blades, and resilient filaments extending about said pulleysr to the lens axis, an electrical 12. An automatic lens diaphragm comprising an electrical measuring instrument having a pinrality of moving coils having axes parallel to the lens axis, a plurality of shafts parallel to the lens axis, a diaphragm blade carried by each coil and each shaft, and means connecting said coils to each other and to said blades for simultaneous angular displacement thereof; said means comprising an operating member on each coil and each shaft, and filaments extending between and anchored to adjacent operating members.

13. An automatic lens diaphragm comprising an electrical measuring instrument having a plurality of moving coils having axes parallel to the lens axis, a plurality of shafts parallel to the lens axis, a diaphragm blade carried by each coil and each shaft, a pulley on each coil and each shaft, and resilient filaments extending between and secured to adjacent pulleys.

14. An automatic lens diaphragm comprising an instrmnent having two coils on axes parallel to and symmetrically arranged with respect to the lens axis, a pair of shafts parallel to the lens axis and symmetrically arranged with respect to the lens axis and the coils, a diaphragm blade carried by each coil and each shaft, a pulley carried by each coil and each shaft, and resilient filaments extending between and secured to adjacent pulleys.

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